PYEONGCHANG, South Korea — It was a moment that may well define these Olympic Games: First came smiling athletes walking side by side under a flag of Korean unity. Then the air was filled with a well-known ballad of sorrow and separation.

And finally, the stadium was full of people standing and cheering Friday in what the Olympic hosts hope could stir a movement toward easing the hair-trigger tensions on the divided Korean Peninsula.

Every Olympics has its share of geopolitical backstories. But organizers of the Winter Games in PyeongChang — which opened Friday in a spectacle laden with lore and symbols binding North and South Korea — have billed them as a generational chance to find a new path for neighbors frozen in a Cold War-era standoff.

Yet obstacles were evident even amid the outreach. The top U.S. envoy to the Games, Vice President Pence, sat stone-faced as the crowd erupted in cheers for the unified Korean team — showing the rift between Washington and its South Korean ally over how to deal with the North’s nuclear and military ambitions.

At the Opening Ceremonies of the Olympics on Feb. 9, Vice President Pence was seated near Kim Yo Jong, North Korean leader Kim Jong Un’s younger sister, and did not applaud when North and South Koreans marched together. (The Washington Post)

The cheering came when athletes from North and South Korea walked together into Friday’s Opening Ceremonies under a single Korean flag in a rare display of unity.

The combined teams — dressed in white and introduced simply as “Korea” — entered the stadium under the blue-and-white “unification flag,” which shows the peninsula as one. The PyeongChang hosts cued up “Arirang,” a poignant, centuries-old Korean folk song that is considered an unofficial national anthem.

Two hockey players — one from North Korea and another from the South — took the Olympic torch to South Korean figure-skating superstar Yuna Kim to light the Olympic cauldron.

The Games are taking place just 50 miles from the border with North Korea. About 500 North Koreans, including 22 athletes, have traveled south for the Games, which will wrap up Feb. 25.

But Pence did not join the joyous welcome for Korean detente: He remained seated with his wife, Karen Pence, and Japanese Prime Minister Shinzo Abe, while others in the VIP box rose to cheer the Koreans.

Those on their feet included South Korean President Moon Jae-in and the two senior North Koreans sent to the Opening Ceremonies — Kim Yo Jong, the sister of leader Kim Jong Un, and Kim Yong Nam, North Korea’s nominal head of state.

Kim Yo Jong, the younger sister of North Korean leader Kim Jong Un, arrived in South Korea with the North Korean delegation on Feb. 9 for the Winter Olympics. (Reuters)

The North Korean pair was seated almost directly behind the Pences, but there was no interaction between them.

Earlier, Pence did not sit down for dinner at a reception for dignitaries that Moon hosted before the opening, instead eating with the American athletes. But Pence did stop by the reception and greeted everyone at the top table — except Kim Yong Nam, according to a South Korean presidential spokesman.

Pence “did not come across” the North Koreans at the reception, a Pence spokesman said.

The vice president’s deliberate snub to the North Koreans — and, by extension, the host country — highlighted the deep divisions between Washington and Seoul on how to deal with Pyongyang.

Moon promotes the Olympics as the “Peace Games” and hopes to use North Korea’s participation as a springboard to better relations between the estranged neighbors — and perhaps to broader denuclearization talks.

Moon warmly greeted Kim Yo Jong at Friday’s ceremony. He will host her and the other senior North Korean officials for lunch Saturday.

Also in the North’s delegation is Choe Hwi, a senior official blacklisted by the United Nations. Seoul had to seek a special U.N. exemption for Choe to spend three days in South Korea.

Choe and Kim Yo Jong also are under direct U.S. sanctions for human rights abuses related to their roles in censoring information in North Korea.

In stark contrast to Moon’s outreach, Pence called North Korea “the most tyrannical regime on the planet” earlier Friday, when he visited a memorial to 46 sailors who died when the Cheonan, a South Korean naval corvette, was sunk by a North Korean torpedo in 2010. Pence also heard from North Korean defectors.

Pence has been waging a campaign to stop Pyongyang from “hijacking” the Olympics with its charm offensive.

He attended the Cheonan memorial with Fred Warmbier, the father of University of Virginia student Otto Warmbier, who died last year shortly after North Korea sent him home in a coma after 17 months of detention for stealing a propaganda poster. Fred Warmbier also attended the Opening Ceremonies, although he did not sit in the VIP box.

Moon, however, left no doubt about his aspirations for the Games.

“Had it not been for the PyeongChang Olympics, some of us might not have had chance to be together in the same room,” the South Korean president said at the reception for VIPs before the Opening Ceremonies. Pence waited outside while Moon spoke because he was late, according to a spokesman for South Korea’s presidential Blue House.

“However, what is more important than anything else is that we are all here together now; we can cheer for athletes together and talk about our future,” Moon said. “We are here together, and that alone will be a precious starting point for a step forward toward world peace.”

International Olympic Committee President Thomas Bach, who has spoken of growing up in a divided Germany, said the joint Korean team sends “a powerful message of peace to the world.”

The 23rd edition of the Winter Games kicked off with the temperature around freezing, and they could be the coldest Games ever held.

The South Korean organizers built a $60 million, 35,000-seat, pentagon-shaped temporary stadium especially for the Games, but it has no roof. This part of South Korea is known for its wind — so much so that pollock fish, a local delicacy, are hung on lines to dry here in the freezing gusts.

Organizers handed out heat packs for feet and hands, heated seat cushions, blankets and hats to those attending the opening. They also built shelters around the Games’ venues.

South Korea spent about $13 billion on its Olympic effort. Almost 3,000 athletes from 92 countries will compete in 102 medal events across 15 sports.

The Games were unveiled with a dazzling display titled “Peace in Motion.”

Five children from Gangwon, the host province of the Games, represented the five Olympic rings and the five elements — fire, water, wood, metal and earth — traditionally believed to make up the universe.

They were led back in time by a white tiger, an adventure that began with the creation myth of Korea and ended at a glittering gate to the future, symbolizing South Korea’s transformation into a high-tech powerhouse.

Then, 1,000 residents of Gangwon entered the stadium, holding candles in white cups and standing in formation to make a dove of peace.

The candles have particular significance in modern-day South Korea. Moon, the president, was elected after hundreds of thousands of South Koreans took to the streets for weeks on end, holding candlelight vigils to protest the previous president, Park Geun-hye, who was impeached and now is detained while on trial on bribery charges.

Along with the diplomatic problems, there were added headaches for the organizers.

An outbreak of norovirus led to the quarantining of large numbers of staff in the days before the Games’ opening. The number of people infected with the contagious vomiting-and-diarrhea bug had risen to 139 at latest count, with cases reported at three sites. Eleven new cases were reported Friday.

But health officials were very prepared in one area. About 110,000 condoms — a Winter Olympics record — are being distributed to athletes in Pyeong­Chang. That works out to about 37 condoms per athlete.

There was also bad news for Russian athletes just hours before the opening of the games. The Court of Arbitration for Sport denied a last-minute appeal filed by 45 Russian athletes who were hoping for an 11th-hour invitation to the Games.

Ashley Parker in PyeongChang and Brian Murphy in Washington contributed to this report.

Anna Fifield is The Washington Post’s bureau chief in Tokyo, focusing on Japan and the Koreas. She previously reported for the Financial Times from Washington, D.C., Seoul, Sydney, London and from across the Middle East.